Meeting Abstract

P2.151  Monday, Jan. 5  Sensitivity and morphology of the cownose ray electrosensory system BEDORE, C.N.*; KAJIURA, S.M.; Florida Atlantic University; Florida Atlantic University bedorech@gmail.com

The electroreceptors of elasmobranch fishes demonstrate the greatest sensitivity of any known vertebrate electrosensory system. The electroreceptors are spatially distributed to a greater or lesser extent according to the variety of head morphologies in this diverse group. Among the elasmobranchs, the cownose ray, Rhinoptera bonasus, is unique in its possession of a bilobed head morphology with paired extensible cephalic lobes on the ventral surface of the head. These cephalic lobes are extended to closely contact the substratum as the ray searches for benthic prey, This may facilitate prey detection by placing the electroreceptors closer to the source of the prey electric fields during foraging. We tested this hypothesis by quantifying the electrosensory pore distribution of R. bonasus in conjunction with its sensitivity to prey-simulating electric stimuli. Results were compared to a more conventionally shaped ray, the Atlantic stingray, Dasyatis sabina. Rhinoptera bonasus has an average of 786 electrosensory pores on the combined dorsal and ventral surfaces, with a high proportion of these pores (40.5%) occurring on the anterior ventral surface; a distribution much like that of D. sabina. Rhinoptera bonasus demonstrated a detection sensitivity of 10.4 nV/cm +/- 2.8SE to simulated bioelectric fields, also similar to reported values for D. sabina. The similarity in pore distribution and sensitivity, despite the differences in head morphology, reflect the phylogenetic stability of the electrosensory system, an important sensory modality. Unlike the benthically associated D. sabina, R. bonasus is more benthopelagic and may have evolved its unique, extensible, cephalic lobes to enhance benthic prey detection even while the body remains higher in the water column.